Minimizing intravascular magnetic resonance imaging (MRI) guidewire heating with single layer MRI transmit/receive radio frequency coil

Abstract

A method for controlling an interventional magnetic resonance imaging (iMRI) system configured to control a heating mode of an iMRI guidewire, the method comprising: controlling, during an iMRI procedure, a magnitude of an induced current in a single-layer MRI radio frequency (RF) coil used in the iMRI procedure, or a phase of the induced current by adjusting at least one of: a difference between a working frequency of a whole body coil (WBC) used in the iMRI procedure and a resonant frequency of the single layer MRI RF coil, a coil loss resistance of the single layer MRI RF coil, or a blocking impedance of an LC circuit connected in parallel with the single-layer MRI RF coil; and controlling a heating mode of the guidewire based, at least in part on the magnitude or phase.

What is claimed is: 
     
       1. A single-layer magnetic resonance imaging (MRI) radio frequency (RF) coil array element configured to operate in a transmit (Tx) mode and a receive (Rx) mode during an interventional MRI (iMR) procedure, the single-layer MRI RF coil array element comprising:
 an LC coil; 
 a matching and Tx/Rx switch circuit operably connected to the LC coil; 
 a preamplifier operably connected to the matching and Tx/Rx circuit; and 
 a magnitude/phase control component operably connected to the LC coil; 
 where the LC coil includes at least one inductor and at least one capacitor, where the at least one inductor and the at least one capacitor resonate at a first frequency; 
 where the matching and Tx/Rx switch circuit, when operating in Tx mode, electrically isolates the LC coil from the preamplifier upon the LC coil resonating with a primary coil, where the primary coil has a working frequency; 
 where the LC coil, upon resonating with the primary coil, generates a local amplified Tx field based on an induced current in the LC coil, the induced current generated by inductive coupling between the LC coil and the primary coil; 
 where a magnitude of the induced current or a phase of the induced current is independently adjustable; 
 where the magnitude of the induced current or the phase of the induced current is configured to be varied over a range of magnitudes or phases respectively; 
 where the matching and Tx/Rx switch circuit, when operating in Rx mode, electrically connects the LC coil with the preamplifier; and 
 where the magnitude/phase control component is configured to adjust the magnitude of the induced current or the phase of the induced current at the LC coil by adjusting impedance of the LC coil while the LC coil is wirelessly electrically coupled to a transmitter through the primary coil. 
 
     
     
       2. A single-layer magnetic resonance imaging (MRI) radio frequency (RF) coil array configured to operate in a transmit (Tx) mode or in a receive (Rx) mode during an interventional MRI (iMRI) procedure, the single-layer MRI RF coil array comprising:
 a plurality of single-layer MRI RF coil array elements, where a single-layer MRI RF coil array element of the plurality of single-layer MRI RF coil array elements comprises:
 an LC coil; 
 a matching and Tx/Rx switch circuit operably connected to the LC coil, where the matching and Tx/Rx switch circuit is a capacitive matching and Tx/Rx switch circuit or an inductive matching and Tx/Rx switch circuit; 
 a preamplifier operably connected to the matching and Tx/Rx circuit; and 
 a magnitude/phase control component operably connected to the LC coil; 
 where the LC coil includes at least one inductor and at least one capacitor, where the at least one inductor and the at least one capacitor resonate at a first frequency, and where the at least one capacitor comprises a first capacitor; 
 where the matching and Tx/Rx switch circuit, when operating in Tx mode, electrically isolates the LC coil from the preamplifier upon the LC coil resonating with a primary coil, where the primary coil has a working frequency; 
 where the LC coil, upon resonating with the primary coil, generates a local amplified Tx field based on an induced current in the LC coil, the induced current generated by inductive coupling between the LC coil and the primary coil; 
 where a magnitude of the induced current or a phase of the induced current is independently adjustable; 
 where the magnitude of the induced current or the phase of the induced current is configured to be varied over a range of magnitudes or phases respectively; 
 where the matching and Tx/Rx switch circuit, when operating in Rx mode, electrically connects the LC coil with the preamplifier; and 
 where the magnitude/phase control component is configured to adjust the magnitude of the induced current or the phase of the induced current, where adjusting the magnitude of the induced current or the phase of the induced current adjusts a heating mode of an iMRI guidewire employed during the iMRI procedure, where the magnitude/phase control component comprises a first switch and a first resistive or reactive component bordering the LC coil, where the first switch is configured to electrically couple the first resistive or reactive component in parallel with the first capacitor while in an ON state and to remove the first resistive or reactive component from in parallel with the first capacitor while in an OFF state, and where the magnitude/phase control component is configured to adjust the magnitude or phase while in Tx mode by changing the first switch between the ON and OFF states. 
 
 
     
     
       3. An interventional magnetic resonance imaging (iMRI) apparatus, comprising:
 a controller; 
 a whole body coil (WBC); 
 an intravascular guidewire; and 
 a single-layer MRI radio frequency (RF) coil operably connected to the controller; 
 where the controller provides the single-layer MRI RF coil with a current, a voltage, or a control signal; 
 where the single-layer MRI RF coil includes a plurality of receive (Rx) loops, where a member of the plurality of Rx loops comprises a PIN diode, a first capacitor, a second capacitor, and an induced current magnitude/phase control component, 
 where the single-layer MRI RF coil is configured to operate in a Rx mode and in a transmit (Tx) mode, where the single-layer MRI RF coil operates in the Tx mode upon the injection of a DC bias into the PIN diode, where the DC bias forward biases the PIN diode, 
 where the single-layer MRI RF coil inductively couples with the WBC when operating in the Tx mode, 
 where the single-layer MRI RF coil, upon resonating with the WBC in Tx mode, induces a uniform local amplified Tx field, where the uniform local amplified Tx field is based, at least in part, on an induced current in the single-layer MRI RF coil, 
 where the induced current magnitude/phase control component controls a difference between a working frequency of the WBC and a resonant frequency of the single-layer MRI RF coil, a coil loss resistance of the single-layer MRI RF coil, or a blocking impedance of an LC circuit connected in parallel with the single-layer MRI RF coil, 
 where a magnitude of the induced current or a phase of the induced current is independently adjustable based, at least in part, on at least one of the difference, the coil loss resistance, or the blocking impedance; and 
 where the magnitude of the induced current or the phase of the induced current controls a heating mode of the intravascular guidewire, 
 where the induced current magnitude/phase control component comprises a first circuit leg and a second circuit leg, where the first and second circuit legs each comprises a diode switch and an electronic component electrically coupled in series with the diode switch, where the first circuit leg is electrically coupled in parallel with the first capacitor, where the second circuit leg is electrically coupled in parallel with the first or second capacitor, where the electronic component is a resistor, a capacitor, or an inductor, and where the controller is configured to control ON/OFF states of the diode switch of the first circuit leg and the diode switch of the second circuit leg to change the phase and/or the magnitude of the induced current in the Tx mode. 
 
     
     
       4. The single-layer MRI RF coil array element of  claim 1 , where the magnitude/phase control component is configured to, upon the single-layer MRI RF coil array element operating in Tx mode, adjust the magnitude of the induced current or the phase of the induced current by shifting the first frequency of the LC coil relative to the working frequency of the primary coil. 
     
     
       5. The single-layer MRI RF coil array element of  claim 1 , where the magnitude/phase control component is configured to, upon the single-layer MRI RF coil array element operating in Tx mode, adjust the magnitude of the induced current or the phase of the induced current by decreasing the induced current. 
     
     
       6. The single-layer MRI RF coil array element of  claim 5 , where the magnitude/phase control component is configured to decrease the induced current by operating as a parallel resonant circuit when in Tx mode. 
     
     
       7. The single-layer MRI RF coil array element of  claim 6 , where the magnitude/phase control component comprises an inductor and a PIN diode connected in parallel with a first member of the at least one capacitor, where the first member of the at least one capacitor has a higher capacitance than a second, different member of the at least one capacitor, where the single-layer MRI RF coil array element operates in Tx mode upon the injection of a DC bias into the PIN diode, where the DC bias forward biases the PIN diode. 
     
     
       8. The single-layer MRI RF coil array element of  claim 1 , where the matching and Tx/Rx switch circuit is a capacitive matching and Tx/Rx switch circuit. 
     
     
       9. The single-layer MRI RF coil array element of  claim 1 , where the matching and Tx/Rx switch circuit is an inductive matching and Tx/Rx switch circuit. 
     
     
       10. The single-layer MRI RF coil array element of  claim 1 , where the LC coil includes at least one conductor, where the at least one conductor is a flexible co-axial cable. 
     
     
       11. The single-layer MRI RF coil array element of  claim 1 , further comprising a shunt PIN diode having a first terminal connected to a first input terminal of the preamplifier, and a second terminal connected to a second input terminal of the preamplifier, where, upon application of a forward bias to the shunt PIN diode, the shunt PIN diode provides shunt protection to the preamplifier. 
     
     
       12. The single-layer MRI RF coil array element of  claim 1 , where the at least one capacitor comprises a first capacitor and a second capacitor, where the magnitude/phase control component comprises a first diode switch, a second diode switch, a first electronic component, and a second electronic component, where the first diode switch and the first electronic component have individual first terminals electrically shorted together and further have individual second terminals electrically shorted respectively to a first terminal of the first capacitor and a second terminal of the first capacitor, where the second diode switch and the second electronic component have individual first terminals electrically shorted together and further have individual second terminals electrically shorted respectively to the first terminal of the first capacitor and the second terminal of the first capacitor, and where each of the first and second electronic components is a resistor, a capacitor, or an inductor. 
     
     
       13. The single-layer MRI RF coil array element of  claim 12 , where the first diode switch comprises a pair of first PIN diodes, and where the first PIN diodes have individual anodes electrically shorted together and have individual cathodes respectively and electrically shorted to the first terminal of the first electronic component and the first terminal of the first capacitor. 
     
     
       14. The single-layer MRI RF coil array of  claim 2 , where the magnitude/phase control component is configured to, upon the single-layer MRI RF coil array element operating in Tx mode, adjust the magnitude of the induced current or the phase of the induced current by adding coil loss to the LC coil. 
     
     
       15. The single-layer MRI RF coil array of  claim 14 , where the first switch and the first resistive or reactive component are respectively a PIN diode and a resistor, where the single-layer MRI RF coil array element operates in Tx mode upon the injection of a DC bias into the PIN diode, where the DC bias forward biases the PIN diode. 
     
     
       16. The single-layer MRI RF coil array of  claim 2 , where the at least one capacitor further comprises a second capacitor, where the first switch and the first resistive or reactive component are respectively a PIN diode and an inductor, where the first capacitor has a higher capacitance than the second capacitor, where the single-layer MRI RF coil array element operates in Tx mode upon the injection of a DC bias into the PIN diode, where the DC bias forward biases the PIN diode. 
     
     
       17. The single-layer MRI RF coil array of  claim 16 , where the magnitude/phase control component introduces a blocking impedance of less than one-hundred Ohms to the LC coil when the single-layer MRI RF coil array element operates in Tx mode. 
     
     
       18. The single-layer MRI RF coil array of  claim 2 , where the at least one capacitor comprises a second capacitor, where the magnitude/phase control component further comprises a second switch and a second resistive or reactive component, where the second switch is configured to electrically couple the second resistive or reactive component in parallel with the second capacitor while in an ON state and to remove the second resistive or reactive component from in parallel with the second capacitor while in an OFF state, and where the magnitude/phase control component is configured to adjust the magnitude or the phase while in Tx mode by further changing the second switch between the ON and OFF states. 
     
     
       19. A non-transitory computer-readable storage device storing computer executable instructions that when executed by a computer control the computer to perform a method for controlling a heating mode of an interventional magnetic resonance imaging (iMRI) guidewire, the method comprising:
 controlling, during an iMRI procedure, a magnitude of an induced current in a single-layer MRI radio frequency (RF) coil used in the iMRI procedure, or a phase of the induced current, by adjusting at least one of:
 a difference between a working frequency of a whole body coil (WBC) used in the iMRI procedure and a resonant frequency of the single-layer MRI RF coil, 
 a coil loss resistance of the single-layer MRI RF coil, or 
 a blocking impedance of an LC circuit connected in parallel with the single-layer MRI RF coil; and 
 
 controlling a heating mode of the iMRI guidewire based, at least in part on the magnitude or the phase; 
 where the single-layer MRI radio frequency (RF) coil comprises an inductor-capacitor (LC) coil, wherein the LC coil comprises a first capacitor, where the controlling of the magnitude or the phase and the controlling of the heating mode comprises adding a first electronic component in parallel with the first capacitor, or removing the first electronic component from in parallel with the first capacitor, at the LC coil, and where the first electronic component is a resistor, a capacitor, or an inductor. 
 
     
     
       20. The iMRI apparatus of  claim 3 , where the first and second circuit legs each consists of the diode switch and the electronic component electrically coupled in series with the diode switch, and where the controller controls the diode switch of the first circuit leg and the diode switch of the second circuit leg so only one diode switch is ON at any given time in the Tx mode. 
     
     
       21. The non-transitory computer-readable storage device of  claim 19 , where the LC coil further comprises a second capacitor, where the controlling of the magnitude or the phase and the controlling of the heating mode comprises adding a second electronic component in parallel with the first or second capacitor, or removing the second electronic component from in parallel with the first or second capacitor, at the LC coil, and where the second electronic component is independent of the first electronic component and is a resistor, a capacitor, or an inductor. 
     
     
       22. The non-transitory computer-readable storage device of  claim 21 , where the adding and the removing of the first electronic component are performed by respectively forward biasing and reverse biasing a first PIN diode electrically coupled directly to the first electronic component, and where the adding and the removing of the second electronic component are performed by respectively forward biasing and reverse biasing a second PIN diode electrically coupled directly to the second electronic component.